GENEVA — International envoy Lakhdar Brahimi expressed little hope for a political solution for Syria anytime soon after meeting Friday with senior Russian and U.S. diplomats trying to bring an end to the civil war, which has claimed tens of thousands of lives.

Brahimi, who is the joint U.N.-Arab League envoy for Syria, spent the day at the United Nations’ European headquarters meeting with Russian Deputy Foreign Minister Mikhail Bogdanov and U.S. Deputy Secretary of State William Burns.

“We are very, very deeply aware of the immense suffering of the Syrian people, which has gone on for far too long,” Brahimi told reporters. “And we all stressed the need for a speedy end to the bloodshed, to the destruction and all forms of violence in Syria.

But he acknowledged that “if you are asking me whether a solution is around the corner, I’m not sure that is the case.”

Brahimi had led them off to lunch after more than an hour of closed discussions, with Bogdanov and Burns talking among themselves as they and their entourages navigated the U.N. corridors. But after meeting for about four hours, the talks ended Friday mid-afternoon without any apparent deal. Bogdanov and Burns left without making any public comment.

Russia has blocked several U.N. resolutions aimed at pressuring Syrian President Bashar Assad, but Moscow says it is not propping up his regime. Recently, top Russian officials have signaled they are resigned to Assad eventually losing power.

But Brahimi defended Moscow’s role.

“I’m absolutely certain that the Russians are as preoccupied as I am, as preoccupied as the Americans are, by the bad situation that exists in Syria and its continuing deterioration,” he said. “And I am absolutely certain that they would like to contribute to its solution.”

Brahimi said the foundation for a political solution continues to be the agreement reached among major powers in Geneva in June, which called for creation of a new governing body for Syria that would “exercise full executive powers” during an unspecified transition period.

“And we agreed that full executive powers means all the powers of state,” Brahimi said of Friday’s discussions. “I will continue to engage all Syrian parties as well as other stakeholders in the region and internationally.”

The conflict began in March 2011 with peaceful protests against Assad’s family dynasty, which has ruled the country for four decades, but the intense crackdown on the uprising and armed rebel opposition soon became a civil war.

The U.N. says at least 60,000 people have been killed in the war and millions have fled their homes. So far, all international efforts to end the fighting have failed. Syria has complained that Brahimi exhibited “flagrant bias” after he called for real, not cosmetic, change in Syria and said Assad was resisting the aspirations of his people.

The U.N. refugee agency said Friday that it is concerned about the severe winter conditions faced by about 612,000 Syrian refugees in Jordan, Lebanon, Turkey, Iraq and Egypt, and there has been no letup in the flow of thousands of people a day across the borders.

“Many of those arriving have been barefoot, with their clothing soaked, and covered in mud and snow,” agency spokesman Adrian Edwards told reporters in Geneva, referring to new refugee arrivals in Jordan.

Friday’s meeting coincided with ground action in Syria during which Islamic militants took full control of a strategic northwestern air base. Activists said the militants seized helicopters, tanks and multiple rocket launchers from the base, which has been the biggest staging area for the government to distribute supplies to its troops and to bomb rebel-held areas in Syria’s north.

The seizure was part of the rebels’ campaign to topple the Syrian government’s air supremacy. The base is near a highway between the capital, Damascus, and the northern city of Aleppo, a major front in the civil war.